OO-D-2855
withstand the imposed loads. The mast shall be furnished with a drill steel
storage rack suitable for racking up to three 12-foot (3.7 m) sections. A mast
cradle shall be provided to support the mast when lowered for transit.
3.13 Drifter. The drifter shall be the variable stroke and variable speed
type. The drifter shall be hydraulically actuated and shall produce not less
than 250 pound-force foot (339 newton meters (N.m)) or torque at rated hydraulic
system pressure. Percussion blows shall be variable, by the operator, to
provide 125 pound-force foot (169 N.m), 150 pound-force foot (203 N.m), 175
pound-force foot (237 N.m), and 200 pound-force foot (271 N.m) per blow to the
drill steel. Maximum power, at rated hydraulic system pressure, shall be not
less than 500,000 pound-force foot (6779 N.m) per minute. Speed shall be
infinitely variable from O - 150 revolutions per minute (rpm). Means shall be
provided for permitting pressurized air to enter the drilled hole for blowing
purposes. The chuck shall be designed to prevent the shank from leaving the
drifter and shall be hardened for high wearing quality and shall be furnished
with a sealed end cap with a water swivel.
3.13.1 Drill steel and bits.
When specified (see 6.2), drill unit shall be
furnished with the following:
Sectional drill rod 1-1/2
inch by 10 foot
(38 mm by 3 m) sections
-
20 each
Drill shanks
-
5 each
Water swivel
-
2 each
Coupling drill steel
-
10 each
Bits - 2-1/2 inch (64 mm)
carbide button
-
8 each
Bits - 2-3/4 inch (70 mm)
carbide button
-
8 each
Bits - 3-1/2 inch (89 mm)
carbide button
-
8 each
Drill bits shall be the carbide button type.
Thread shall be I.R. 38 tandem
thread.
3.14 Controls. All controls shall be clearly marked as to use and function.
The tramming, boom, and mast controls shall be grouped for safe operation and
ease of operation when positioning the drill, boom, and mast preparatory to
drilling. The drilling controls shall be grouped for safe operation and shall
be accessible to the operator when drilling at any position. Drilling controls
shall operate the rock drill functions including the rotation, feed, and
flushing operations.
3.15 Hydraulic system. The hydraulic system shall be protected against the
entrance of dirt or other foreign materials and shall be complete with all
operating accessories, including a pump, hydraulic cylinders, hydraulic motors,
10- to 25-gallon (38- to 95-liter (L)) minimum reservoir, relief valves, 25
minimum micron suction and discharge filters, check valves, and an oil cooler.
The supply pump shall be the manufacturer's standard pump, capable of supplying
sufficient hydraulic oil at rated system pressure, as required, to energize
hydraulically powered components. A hydraulic oil cooler shall be provided.
Pressure compensated flow control valves shall be provided to control hydraulic
functions. A wiper shall be provided on all hydraulic cylinders adjacent to the
piston rod seal to prevent dirt and abrasives from damaging the seal or entering
the cylinder. When a gear type pump is used, the hydraulic system shall include
manufacturer's recommended filters.
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